Read "Into a Desert Place" by Graham McIntosh. He walked all the way around Baja California, on the coast. A large part of his drinking water he got by boiling seawater in a plain old tea kettle with a few coils of stainless steel tubing running out of the whistle hole...

He has apparently written three more books on the subject, the most recent titled "Marooned With Very Little Beer." I haven't read any of those yet...